Derivative Instruments and Hedging Activities - Notional principal amounts (Details) $ in Thousands	12 Months Ended
Sep. 30, 2019 USD ($) building	Sep. 30, 2018 USD ($)
Two Buildings on Existing Campus
Derivative Instruments and Hedging Activities
Unrealized gain (loss) on derivative	$ 200
Number of building under lease \| building	2
Lease term	5 years
Instruments designated as accounting hedges: \| Foreign currency forwards
Derivative Instruments and Hedging Activities
Notional principal outstanding derivative instruments	$ 143,164	$ 169,406
Instruments designated as accounting hedges: \| Interest Rate Swaps
Derivative Instruments and Hedging Activities
Notional principal outstanding derivative instruments	95,000
Instruments not designated as accounting hedges: \| Foreign currency forwards
Derivative Instruments and Hedging Activities
Notional principal outstanding derivative instruments	24,220	27,909
Notional principal outstanding derivative instruments designed to manage exposure	14,000	14,700
Unrealized gain (loss) on derivative	$ 0	$ 200

Aggregate notional amount specified by the derivative(s) designed to manage exposure. Expressed as an absolute value.

No definition available.

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- Definition

The number of building under lease agreement.

+ References

No definition available.

+ Details

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

+ Details

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- Details

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- Details

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- Details

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- Details

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